Out in the vast oil fields of West Texas there are many wellbores formed which extend thousands of feet down into the ground. These wellbores are filled with a sufficient head of mud so that the pressure effected by the gaseous hydrocarbons are thereby contained within the pay zone. A casing is cemented into place thereby sealing each of the overlying formations from one another and preventing contamination of various different zones of various different substances with one another. Thereafter a casing gun is run downhole and one or more hydrocarbon containing formations communicated with the wellbore by means of perforations which are formed through the casing, cement, and back up into the pay zone. It is customary to next run a tubing string downhole into proximity of the perforations, and then the annulus above the end of the tubing string is packed off. The interior of the tubing must next be swabbed to remove the mud therefrom, thereby reducing the hydrostatic head effected by the mud upon the pay zone so that when the hydrostatic head is reduced to a value which is less than the bottom hole pressure exerted by the formation, production of hydrocarbons commences from the pay zone, through the perforations, into the lower borehole, into the bottom of the tubing string, and up through the string to the surface of the earth where the production is tied into a suitable gathering system.
It is expensive to move a swabbing crew along with a workover rig onto the well site, and for this reason it would be advantageous to have made available both method and apparatus by which the tubing string could be run dry into the perforated borehole so that after the string was properly positioned and the packer set, the tubing could be open to flow, whereupon the necessity of the expensive swabbing crew and the costly workover rig would be eliminated.
Some prior art solutions to the above problems and desires are known, for example, Bramlett U.S. Pat. No. 3,095,040 uses a go-devil for rupturing a break off-plug. Moller U.S. Pat. No. 3,029,875 drops a weighted object to dislodge a plug from a pipe. Layton U.S. Pat. No. 2,903,074; Kinley U.S. Pat. No. 2,922,479; and Courtney U.S. Pat. No. 3,003,565 each disclose a device for establishing communication between a tubing string and the casing by dropping a weighted object. U.S. Pat. No. 3,931,855 shows a plug in combination with other well completion apparatus and teaches a method of completing a well. The present invention represents an advancement over the above related art.